


Mine, Yours

by Dustinthemadhattercp



Series: Haikyuu!! Siblings [1]
Category: Haikyuu!!
Genre: Anal Sex, Blow Jobs, Fluff, Jealousy, M/M, Made Up Siblings, Oikawa Being An Idiot, Oikawa Having A Little Brother, Sibling Rivalry, Surprise Ending
Language: English
Status: Completed
Published: 2017-09-05
Updated: 2017-09-05
Packaged: 2018-12-24 04:03:20
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,530
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12004608
Author URL: https://archiveofourown.org/users/Dustinthemadhattercp/pseuds/Dustinthemadhattercp
Summary: Oikawa is worried his younger brother is crushing on his boyfriend, and is trying to steal him from him. Of course, Iwaizumi is having none of it, and tells Oikawa to prove that he's the setter's, if he must.Truth is, Iwaizumi is just looking for sex.





	Mine, Yours

**Author's Note:**

> Ah, back again with another one shot, but still can't update on the multi-chapter fanfic. 
> 
> Way to go.
> 
> Like every other fanfiction, this was created with the same friend, in school. Still wondering how we ever pass our classes like this. We created siblings for the Haikyuu!! Characters, because we can.

“You did what?!” Oikawa stared in disbelief at the brand new Aoba Jōsai jersey his younger brother, Katsuki, had brought home. On the back of the item in question was a gleaming, light blue number four; the same number his Iwa-chan used to have the year prior, before they graduated. 

“Hmm? I asked for the number four, and I got the number,” the second year explained casually. Oikawa narrowed his eyes at his brother. The boy had always been fond of his best friend-- now boyfriend --but the golden-eyed setter was beginning to believe it was definitely more than _just_ admiration. 

“Is there something wrong with it?” Katsuki asked. “I thought it was pretty cool. What do you think, Hajime?” His dark brown orbs swept over to where Iwaizumi was lounging on the sofa, straw from a juice pouch at his lips. The hitter shrugged and gazed nonchalantly at Oikawa. 

“It’s a number. I don’t really see all the fuss over it.” Toru crossed his arms over his chest, pouting like a child. 

“You’re so oblivious, Iwa-chan! Katsuki is obviously after you!” This had his brother quirking an eyebrow in question, but Oikawa didn’t miss the slight blush that appeared on the younger’s cheeks after he pointed it out. Oikawa fumed at the way Iwaizumi didn’t even flinch at his words, like if he expected it, or that he just didn’t care.

The brunette flopped onto the couch, arms locking around the hitter’s waist. “Don’t you care at all? I’m just trying to protect you from him!”

Iwaizumi responded with an annoyed look, “All you’re doing is whining.” Oikawa groaned and buried his face in his boyfriend’s chest. 

“You don’t care about my feelings on this?” Iwaizumi rolled his eyes and sighed, but ran a soothing hand through the other’s hair. 

“It’s not that, I just don’t see why it’s such a big deal. It’s a shitty jersey with a number.” It was a huge deal to Toru. 

His brother had always _admired_ Iwaizumi, and tried to be like him, _impress_ him in any way possible. When they were younger, the boy had even tried to style his hair like the hitter, but it fell flat on his head like it usually did, looking eerily similar to the little King, Kageyama’s hair style. 

In junior high, Katsuki had become a hitter on his school’s volleyball team, saying he wanted to be “a great hitter like Hajime”. Another reason: his brother called him Hajime! 

Katsuki took the hint from the overwhelming tone in the room. “You both talk things out. I’m going to invite Manabu over.”

Toru looked up from his spot on Iwaizumi’s chest. “No way! Not until you admit that you--wait, who’s Manabu?” Katsuki rolled his eyes, walking out of the room. He knew it wasn’t worth the time to answer. Katsuki was gone in a few seconds, and then it was just the two university students left in the room. 

Iwaizumi brushed his thumb over Oikawa’s cheek to get his attention. “Care to explain to me why you’re so pissed off at your brother?”

Oikawa frowned, “Because he’s a predator and you're his prey, Iwa-chan!” Hajime tilted his head, completely dumbfounded. Toru began to explain, “ He always tries to be like you, and I’m pretty sure his ‘admiration’ that he says he has for you is actually a crush! Katsuki is trying to steal my Iwa-chan away from me and I don’t like it!”

“That is….ridiculous,” Iwaizumi replied. The brunette gaped at him, a bit hurt. “He can’t steal me from you if I’m not interested in being stolen.” Oikawa blushed slightly when the dark haired man pressed a quick kiss to the corner of his mouth. 

“You say I’m yours?” Toru nodded. “Then prove it.” 

_That little--_

Oikawa went to kiss that lust-filled smirk off Iwaizumi’s face when the other held a finger to the brunette’s lips. “In your room, Toru.” He pouted for about a second before bounding off Iwaizumi’s lap and tugging him toward his bedroom in the back of the apartment that he shared with Katsuki. 

Neither of them noticed said boy grimacing in his doorway, aware of what they were about to do. 

Once they were in the room, Oikawa was kicking the door closed and tugging Iwaizumi in for a blistering kiss. The shorter of the two slammed Toru against the wall, forearms on it as he caged his boyfriend between his arms. 

Oikawa wasn’t giving Hajime a chance to react before his tongue pushed past the man’s lips and into his mouth. A groan came from both men when their tongues twisted together in a raging battle for dominance, which Iwaizumi won easily, like usual. The hitter decided immediately that his setter tasted like honey, most likely the pastries he had bought a few hours prior. 

“Bed,” Iwaizumi demanded, breaking the kiss. The taller man wasn’t hesitant when he led them to the small twin in the corner, dropping himself onto the creaking mattress, almost like a dance he’d memorized over the years of their relationship. The familiarity of the worn sheets brushing against his skin, and the groaning wood of the bed frame below them was what Oikawa loved, and hoped Iwaizumi appreciated as well. 

Hajime was already trying to pull off the setter’s sweater, making the brunette chuckle. “Patience, Iwa-chan. We have all the time we want.”

To which, Iwaizumi replied with, “I will rip it off.” Toru only rolled his eyes in amusement and aided the man in the task of getting his top off his body, and onto the floor. Hajime’s mouth was soon on one of his nipples, and Oikawa let out a pleasured breath when his teeth tugged at the pert nub. 

Nimble fingers tangled in spikey locks, twisting when Iwaizumi used his teeth on Oikawa’s sensitive chest. Toru soon felt that this just wasn't enough. Wasn’t this supposed to be a way to show that Iwaizumi was _his_? 

He took the chance to flip the situation, actually _flipping_ their positions so that the hitter was sprawled under him, eyes wide with the sudden action. He was about to protest when Oikawa pressed a finger to his lips, eyes flashing with a newfound amusement. “I will rip it off,” The brunette mocked, dragging a slim finger down Hajime’s clothed chest, and the hitter narrowed his eyes, almost daring him to do so. 

Iwaizumi was pleasantly surprised when Oikawa actually _did_ rip his shirt off his body with one fluid motion, the brunette giggling with satisfaction as it was dropped onto the floor. _“Much better,”_ he purred, sliding down on his lover’s tanned body. His lips dragged down Hajime’s skin, leaving goosebumps in their wake. 

Oikawa stopped just before the waistband of Iwaizumi’s jeans, tongue darting out to circle the man’s belly button, eventually dipping in. Hajime propped himself up on one elbow, hand twitching as he watched Oikawa’s next movement. 

Toru smirked, sickly sweet, as he dragged his nose over the pronounced bulge in Iwaizumi’s jeans, causing the man’s breathing to stutter just from the sight. “Let me make you feel good, okay, _Iwa-chan_?” His voice was thick with lust, and Hajime’s gut twisted in arousal. Oikawa mouthed at his clothed erection, dampening the front of his jeans with his saliva. 

The brunette unbuttoned and unzipped Iwaizumi’s pants with deft fingers, dragging them (and his underwear) down over the man’s hips and legs, pulling them off and tossing them somewhere in the room. Toru tongue swiped over his lips, dampening them with his pooling saliva as he stared lustfully at Hajime’s twitching length. The head was an angry red, glistening with beading precum. 

Iwaizumi watched the setter with curiosity, eager for him to just _put his mouth on his--_

“Iwa-chan.”

He was broken from his train of thought. Oikawa smirked as he rubbed his cheek against the hitter’s shaft, eyes almost, _almost_ innocent as he did so. “Every part of you is all mine, Hajime. Especially _this_.” 

The man’s lips parted slightly as he flicked his _tongue_ over Iwaizumi’s tip, organ swirling around it like it was his favorite treat. To Oikawa, it was. He proceeded to wrap his pretty, pink lips around Hajime’s member, sliding them down as he took more of his lover into his mouth. 

And when he did that thing with his tongue, it had Iwaizumi letting out a low moan, causing shivers to travel down Oikawa’s spine. The brunette hollowed out his cheeks a bit, sucking deliciously on his boyfriend’s cock, cautious to make sure his teeth didn’t touch, much less press too hard, on his length. He didn't want Iwaizumi to yell at him like he did the first time he gave him head, when Oikawa accidentally used too much teeth when doing it. 

It hadn’t been a pleasurable experience for either of them. 

Hajime cradled Toru’s head as he sunk farther down on his length. When he felt his tip hit the back of Oikawa’s throat, he remembered that his boyfriend didn't exactly have a gag reflex, which caused a broken moan to leave his mouth. 

It was when Oikawa began bobbing his head that Iwaizumi really had to control himself. His breathing was ragged as he tried not to buck his hips. The warmth surrounding him was heaven, and it pleased the setter when he felt Iwaizumi squirm underneath him. 

Soon enough, Oikawa was moving his mouth off of Hajime. The man opened his mouth to protest, but Oikawa shushed him. “I want you to cum inside of me.” Iwaizumi snapped his mouth shut. He wouldn't deny his boyfriend that. _Ever_. 

Oikawa shrugged off his shorts and boxers, throwing them off to the side. His erection was finally out for Iwaizumi to see. The man loved how it was slightly curved toward the brunette’s stomach. It was almost cute, in a way. 

Toru reached a hand behind himself, a finger prodding at his entrance. He snorted when Iwaizumi glowered at him for not letting him see. He adjusted himself so that his hips were swaying in the air, finger breaching his already loose hole. He thanked his past self for the prepping he’d done in the shower that morning. 

Figuring he could take it, he added another finger, twisting them both in _just the right way--_ he couldn’t help when he moaned like a professional porn star. It wasn’t helping that Iwaizumi’s hand had crept in between Oikawa’s thighs, fingers wrapped around his neglected cock. 

The hitter eagerly stroked Toru, stomach fluttering with desire each time the paler man keened with pleasure. “Hajime...need you in me…” he whined, now up to three fingers. Iwaizumi didn’t hesitate to switch their positions, Oikawa’s fingers slipping out in the process. 

Toru let his boyfriend spread his legs to his liking and position his tip at his twitching entrance. He breathed unevenly, eyes darkened with lust and want. “Put it in already!” He hissed, rolling his hips against Iwaizumi’s cock. 

The man swatted the setter’s right buttock with his palm. “Patience, you.” Oikawa whined and went to protest, only to cry out when Hajime’s girthy length breached his entrance. 

Iwaizumi had his head tilted back slightly, eyebrows furrowed as he kept himself from slamming himself inside of the tight heat that engulfed only part of his member. He knew Oikawa could probably take it, but he knew what really pleased his lover the most. The setter loved it when Hajime slowly broke him from the inside out. 

Toru had his hands fisted in the sheets by the time Iwaizumi was fully seated inside the man. His breathing was labored and he was moaning desperately for his lovers cock. He got his wish when Iwaizumi began thrusting, length stroking deep inside him, and _hell_ , could Oikawa feel it in his gut. 

Next time he knew to fuck the foreplay. He was way too close already, and they'd only been at it for two minutes. 

“Fuck-!” Oikawa exclaimed when Iwaizumi increased his speed all of a sudden, hands reaching up to claw at the hitter’s back. He felt arousal pool in his gut at the sight of his boyfriend’s smirk. 

Oikawa saw stars. 

Iwaizumi had found his prostate. That fucking smirk had the brunette’s head swimming, and he could no longer register what was coming out of his mouth. Broken moans and whimpers bubbled from his throat the longer Iwaizumi pleasured him with that wonderful cock of his. The earlier events of the day were long gone from his mind, the only thing occupying it being Iwaizumi and his own blistering pleasure. 

The hitter was his and only his; inside of the bedroom and out. They both knew that, and by the way Oikawa’s moans echoed loudly throughout the room, he guessed his brother knew that too. 

It also proved that Oikawa was completely and utterly--

_“Mine.”_

That one word from Hajime was all it took for Oikawa to erupt all over both of their chests, painting their skin with white. He squeezed around Iwaizumi in an almost vice like way, forcing a groan to fall from the hitter’s lips as he spilled his seed inside of his boyfriend. 

For a few moments, the only thing that could be heard was their erratic breathing. When Iwaizumi went soft, he pulled out, pleased as his cum dripped out of Oikawa. He stood up on shaky legs and made his way into the bathroom that connected to the brunette’s room. He could hear voices from outside. He guessed it was Katsuki and Manabu. Wetting a washcloth, he brought it back over to Oikawa and began wiping the sweat and semen from his lover’s skin. The man hummed with appreciation. 

“You take such good care of me, Iwa-chan.” The dark haired man only grunted in reply, kissing Oikawa’s swollen lips softly. 

Oikawa was soon wrapped up in Iwaizumi’s arms, content with his situation. The tanner man was running his fingers through his sweaty locks. “I have a question,” he spoke suddenly. The brunette looked up at him in confusion. “I still don’t get why you think Katsuki has a crush on me.”

Toru quirked an eyebrow. His mind went back to his brother, when all of a sudden he remembered something. 

“Iwa-chan, Katsuki never told me who Manabu was!”

Iwaizumi rolled his eyes. “So that's why. You do know that Manabu is Katsuki’s boyfriend, right?” By Oikawa’s shocked expression, he guessed he didn’t. “You don't remember Manabu? Manabu Ushijima. Wakatoshi’s little--” He didn’t have a chance to explain anymore before the brunette in his arms was shrugging on his shirt and pants, rushing out of the room. 

Oikawa had ran to where he could hear voices, which was back in the living room. There, on the sofa, was his brother. His precious little brother with a bigger man’s arm slung around his shoulders. Manabu was almost an exact replica of Wakatoshi, only with messier hair and green-hazel eyes. 

Oikawa felt his heart stop with Manabu’s next few words. 

“Katsuki, you should have come to Shiratorizawa.”

He ignored his brother’s confused stare as he dropped to his knees and yelled out, _“Curse you Wakatoshiiiiiii!”_


End file.
